Intralesional BCG injection is one of the most effective methods in provoking tumor regression, although the mechanisms involved are not clearly understood. A single intralesional injection of BCG cell wall vaccine will provoke regression of a naturally occurring carcinoma in an outbred species of animal (bovine ocular squamous cell carcinoma) in 25 to 40% of treated animals. Using this tumor system, the study is designed to determine certain immunological parameters, both peripherally and intralesionally, which are concomitant with, and may be partially responsible for, tumor regression after intralesional BCG cell wall injection. When these parameters are known, immunological maneuvers can be designed to enhance the mechanisms responsible for tumor regression. Since this tumor system is particularly analogous to human head and neck tumors, the information gained will be especially useful.